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IS 2394 (1984) : Code of practice for application of lime 
plaster finish [CED 5: Flooring, Wall Finishing and 
Roofing] 



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PROTECTED BY COPYRIGHT 



Indian Standard 



( Reaffirmed 2001 ) 



CODE OF PRACTICE FOR 
APPLICATION OF L[ME PLASTER FINISH 

( First Revision ) 



UDC 69 002-54 : 693-61 




® Copyright J 984 
INDIAN STANDARDS INSTITUTION 

MAISAK BllAVAN. 9 DAUADUH SllAEl ZAFATl MAHG 

NEW DEuij \\wm 
Gt 5 OctishtT 1984 



18:2394-1984 

Indian Standard 

CODE OF PRACTICE FOR 
APPLICATION OF LIME PLASTER FINISH 



( First Revision ) 



Flooring and Plastering Sectional Committee, BDG 5 

Vhairman 
Shbi O. p. Mittal 
S-252 Panchsila Park 
New Delhi 110017 ' 

Members Representing 

Shri S. K. Banebjbe National Test House, Calcutta 

Shbi P, R, Das ( Alternate) 
Shbi N. BoBALmaiAH Builder's Association of India Limited, Bombay 

Shri Dinbsh a. Ghokshi M/s Arcoy Industrie*, Ahmedabad 

Shrt Rasikdai, A. ChokshiY -4/^#fna*#) 
Deputy Dibeotoii ( Aboh ) Research, Designs and Standards Organization 

( Ministry of Railways ) , Lucknow 
Deputy Director ( B & S ) ( Alternate ) 
Director Maharashtra Engineering Research Institute, 

Nasik 
Research Opfiobr ( Matbriaii 
Testing Division ) ( Alternate ) 
Db V. S. Gupta The Fertilizer ( Planning and Development ) India 

Limited, Sindri ( Bihar ) 
Shri K. V. Gurus wamy Indian Oil Corporation Limited, New Delhi 

Shbi G. V. Pang ark ar ( Alternate ) 
Shbi S. C. Kapoob M/s Modern Tiles & Marble, New Delhi 

Shri A. G. Kapoob ( Alternate) 
Brig D. R. Kathuria The Institution of Engineers ( India ), Calcutta 

Shri K. E. S. Mani The Bhor Industries Limited, Bombay 

Shbi Ramesh D. Patel ( Alternate ) 
Dr Mohan Rai Central Building Research Institute (CSIR), 

Roorkee 
Dr R. K.Jain {Alternate) 
Shbi M. V. Muruqappan M/s Coromandal Prodorite Pvt Ltd, Madras 

Shri R. Srinivasan ( -4/i«maftf ) 

{ConHmudonpageZ) 



O O>0Hght 1984 

INDIAN STANDARDS INSTITUTION 

This publication is protected under the Inman G^j^ri^ Act ( XIV of iS57 ) and 

reproduction in whole or in part by any meaxu exeept Hith written permission of the 

publisher shall be deemed to be an infringement of copyright under the said Act, 



IS : 2394 - 1984 

( Continutd from page 1 ) 

Mtmhen Representing 

Shut Ranjit Singh Ministry of Defence ( DRDO ), New Delhi 

Sma K. A. Suvkaskar ( Alternate ) 
Shiu O. p. Ratra National Buildings Organization, New Delhi 

Shri D. B. Sen Indian Institute of Architects, Bombay 

Shri S. B. Shiromany {Alternate) 
Shri J. K. K. SiNGHANiA Engineer-in-Chief 's Branch, New Delhi 

Maj S. p. Shabma {Alternate) 
Shrt p. Srtnivasan The Concrete Association of India, Bombay 

Shri G. R. Joshi ( Alternate ) 
SopEiaMTKNDiNo ENGINEER PubHc Wofks Department, Government of Tamil 

Nadu 
ExKCUTivE Enoi>T!:er ( Alternate ) 
SnpF.KTNTKNDiNG SURVEYOR OF Central Public Works Department ( GDO ), New 
Works (CZ) Delhi 

Stjrv]':yor or Works ( GZ ) {Alternate) 
Shri G. Raman, Director General, IS I ( Ex-officio Member) 

Director ( Civ Engg ) 

Secretary 

Shri A. K. Avasthy 

Assistant Director ( Civ Engg ), ISI 



Cement Concrete Flooring and Other Miscellaneous 
Works Subcommittee, BDC 5 : 7 

Convener 

Shri O. P. Mittaj. 

S-252, Panchsila Park 

New Delhi 1 10017 

Members 
SiiUi N. BoKAiaXoiAii Builder's Association of India, Bombay 

Shri S. C. Kapoor Modern Tiles & Marble, New Delhi 

Shri A. G. Kapoor ( Alternate ) 
Dr Mohan Rai Central Building Research Institute (CSIR), 

Roorkee 
Shri B. S. Gupta ( Alternate ) 
Shri M. P. Patkar Central Public Works Department, New Delhi 

SuKVEYOn. or Works ( AVN ) ( Alternate ) 
Shri G. C. Sharma Indian Institute of Architects, Bombay 

Shri Naresh Kqcuati (Alternate) 
Shri P N Talwar The Northern India Tiles Corporation, New 

Delhi 
S HR I W . N . T a L w A R [A Iternate ) 
Shri M. G. Virmani Engineer-in-Chief's Branch, Army Headquarters, 

New Delhi 
Shri S. K. Malik ( Alternate ) 



IS : 2394 - 1984 

Indian Standard 

CODE OF PRACTICE FOR 
APPLICATION OF LIME PLASTER FINISH 



( First Revision ) 



0. FOREWORD 

0.1 This Indian Standard ( First Revision ) was adopted by the Indian 
Standards Institution on 31 July 1984, after the draft finalized by the 
Concrete, Flooring and Plastering Sectional Committee had been 
approved by the Civil Engineering Division Council. 

0.2 Lime plaster and allied finishes are commonly used in this country 
for internal finishes as well as for external renderings. But the practice 
regarding the selection of materials, preparation, thickness of coats and 
methods of application vary considerably from region to region and the 
large experience existing with various construction departments is 
reflected in the specifications they have developed. It is the object of this 
standard to cover comprehensively and provide guidance for the practice 
of lime plaster finish suitable to Indian conditions with respect to 
availability of materials and equipment and conditions of exposure. The 
Sectional Committee responsible for formulating this standard has also 
taken into consideration the various specifications presently being followed 
by the Central and State Public Works Department, the Military 
Engineering Service and other construction agencies and reports of the 
National Buildings Organization. 

0.3 This standard was first published in the year 1965. In the present 
revision use of Portland slag cement conforming to IS : 455-1976* and 
Portland pozzolana cement conforming to IS : 1489-1976t have been 
included. Use of fly ash as pozzolana has also been included. 

0.4 For the purpose of deciding whether a particular requirement of this 
standard is complied with, the final value, observed or calculated, 
expressing the result of a test or analysis, shall be rounded off in 
accordance with IS : 2-1960J. Th^ number of significant places retained 
in the rounded off value should be the same as that of the specified value 
in this standard. 



♦Specification for Portland slag cement ( third revisiM ), 
fSpecification for Portland pozzolana dement ( second reviswn ). 
JRules for rounding off numerical values ( nvistd). 



IS : 2394 - 1984 

0.5 This standard is one of a series of Indian Standards covering plaster 
finishes. Other standards published in the series are: 

IS ; 1661-1972 Code of practice for application of cement and 
cement-lime plaster finishers {first revision ) 

IS : 2402-1963 Code of practice for external rendered finishes 

1. SCOPE 

1.1 This standard covers application of lime piaster finish to wails, 
ceilings, columns and similar surfaces on backgrounds suitable for 
receiving lime plaster finish. 

1.2 Recommendations are laid down with regard to the preparation of 
surface to receive plaster and the number of coats to be applied on 
different surfaces under various conditions. Different materials and their 
proportioning with lime for preparation of mortar for different coats are 
also included. 

1.3 The application of this standard, is restricted to only those types of 
plastered finishes in which lime constitutes the main binding material. 

2. TERMINOLOGY 

2.0 Tor the purpose of this standard, the definitions of terms given in 
IS : 10403-1983* and IS : G50B-l972t shall apply. 

3. NECESSARY INFORMATION 

3.1 In the selection of materials for plaster and in their mixing and 
application, information is necessary on the following points and detailed 
consideration shall be given to them before starting plaster work: 

a) Types of surface over which it is proposed to apply plaster so that 
constructional details may be suitably adopted to them and the 
amount of subsequent preparation necessary before plastering 
may be minimized. 

b) Area and types of finish required together with sufficient details 
of the nature of the surface to be plastered. 

c) Details of finish at junctions with doors, windows and other 
openings, ceilings, linings, etc, and at all comers; 



♦Cjlossary of terms relating to building lime finishes. 
tGlossary of terms relating to building lime. 



IS: 2394 -1984 

d) Types of cornice, arris and return treatments desired, and of 
dado treatment where required; 

e) Details of scaffoldings ( staging ) for access to work in the correct 
sequence together with provision for adequate protection of 
adjacent surfaces during plastering operations, particularly in 
ceiling work; 

f ) Details of fixing accessories to be embedded in the plaster; 

g) Types of surface or decorative finish to be applied over the 
plaster and detailed information on the compatibility of the 
plaster with the proposed decorative finish; and 

h) Rainfall and climatic conditions. 

3.2 All information required in 3.1 shall be made available to those who 
are responsible for the plastering work. Necessary drawings and 
instructions for preparatory work shall also be given. 

3.3 Arrangement shall be made for the proper exchange of information 
between those engaged in plastering and all others whose work will affect 
or will be affected. 

4. PROGRAMME OF WORK IN RELATION TO PLASTERING 

4.1 Operations Before Plastering — Building operations, such as 
construction of brick and block walls, the encasement of steel columns 
and beams with concrete, etc, requiring subsequent plastering, shall be 
so programmed that they are sufficiently cured and dry to receive the 
plaster without subsequent damage to plaster or decoration. 

4.1.1 All service pipes, conduits, cables, etc, to be embedded in 
masonry work and covered with plaster shall be completed and suitably 
protected against corrosion, where necessary, before plastering is begun 
and the time of plastering shall be scheduled accordingly. 

4.2 Operations During Plastering — Where other building operations 
are required to proceed simultaneously with plastering, special care shall 
be taken to programme the work so as to cause the minimum amount of 
interference. 

4.3 Plastering operations shall be so scheduled as to allow sufficient 
interval between successive coats. 

4.4 Operations After Plastering — Care shall be taken to ensure that 
subsequent building operations do not cause damage to the plaster work. 



IS : 2394 - 1984 

This may be achieved by careful programming and by the avoidance of 
last minute alternations in the design or in the sequence of work. 

5. MATERIALS, TOOLS AND ACCESSORIES 

5.1 The following materials, conforming to relevant Indian Standards 
shown against them, shall be used: 

Name Conforming to 

a) Lime IS : 712-19731 

b) Pozzolana IS : 1344-198F and IS : 3812-198P 

c) Sand IS : 1542-1977* 

d) Cement IS : 269-1976^ IS : 455-1976« 

IS: 1489-1976^ 

e) Wood lath, Timber IS : 1331-19718 

5.2 The following materials, wherever used shall conform to the relevant 
Indian Standards shown against them: 

a) Lime Putty — This shall be obtained by slaking lime with water 
in accordance with IS : 1635-1975^. 

b) Water — The water used for mixing and curing shall conform to 
the requirements given in 4.3 of IS : 456-1978^** 

c) Natural Fibres — Natural fibres, such as Munj, jute, hemp, 
coconut fibre, hair, if necessary, may be used as admixtures 
with plasters. They shall be clean and free from oil. 

5.3 Tools used for plaster work may be in conformity with 
IS: 1630-1984". 



^specification for building limes ( second revision ). 
^Specification for calcined clay pozzolana ( second revision ), 
^Specification for fly ash for use as pozzolana and admixture {Jirst reviiion ). 
^Specification for sand for plaster {first revision ). 

'Specification for ordinary and low heat Portland cement ( t hi fd revision ). 
^Specification for Portland-slag cement ( third revision ) . 
''Specification for Portland-pozzolana cement {second revision ). 
^Specification for cut sizes of timber ( second revision ). 

^Code of practice for iiled slaking of building lime and preparation of putty 
(first revision ). 

*°Code of practice for plain and reinforced concrete ( third revision ). 
^^Specification for Mason's tools for plaster work and pointing work (first revision). 



IS : 2394 - 1984 

6. STORAGE OF MATERIALS 

6.1 Lime, cement and sand shall be stored as given in IS : 4082-1977* 
and IS : 7969-19751. 

7. CARE OF TOOLS AND ACCESSORIES 

7.1 Cleanliness of the tools is very important as contamination with set 
material can seriously affect the performance as well as reduce the 
affective life of tools. 

7.1.1 All tools shall be cleaned by scrapping and washing at the end of 
each day's work, or after use. Metal tools shall be cleaned and greased 
after each operation. All tools shall be examined and thoroughly 
cleaned before plastering is begun. 

7.2 Sca£Foldin'g ( Staging ) — Wooden bailies, planks, treaties and other 
scaffolding materials shall be sound and in accordance with local building 
regulations. It shall be thoroughly examined before erection and tested 
before use. Steel scaffolding, if used shall conform to IS : 2750- 1964 J and 
used as in IS : 3696 ( Part I )-1966§. 

8. DESIGN CONSIDERATIONS 
8.1 Suitability of Lime Plaster 

8.1.1 Lime plasters are characterized by high workability and are 
generally suited for internal surfaces. Lime mixes have a long working 
time, a slow rate of strength development and reasonable strength. 

8.1.2 Lime plastered finishes are not suitable for external surfaces in 
areas of heavy rainfall, very damp places and in places where extreme 
water tightness is required. 

8.1.3 Plastering mixes, based on hydraulic, semi-hydraulic or fat limes 
may be successfully used both for undercoats and finishing coats, 
provided proper attention is paid to proportioning of various ingredients 
and workmanship. The plaster hardens by drying and by recarbonation. 
This is a slow process and during the early stages after application the 
plaster is rather sensitive to shock and vibration. 



* Recommendations on stacking and storage of construction materials at site 
( first revision ) . 

tSafety code for handling and storage of building materials, 

JSpecification for steel scaffoldings. 

ISafety code for scaffolds and ladders: Part 1 Scaffolds. 



18:2394-1984 

8.2 Resistance to Knocks and Abrasion — Resistance of lime plaster 
to knocks and abrasion is not high but it can be increased by the use of 
coarser grades of fine aggregate and natural fibres in the plaster mix. 
Resistance can also be improved by gauging lime plaster with cement. 

8.3 Suitability for Surface Finishes — Lime plastered surfaces are 
specially suitable for receiving finishes, such as white wash, colour wash, 
distemper, because of better adhesive properties of lime plastered 
surfaces. However, where cement-based paints are to be applied, lime 
plastered surfaces are not suitable. 

8.4 Corrosive Effect on Metals — Metals in contact with lime plaster 
are liable to corrosion. However, when lime- cement plaster of rich mix, 
say 1 : 1 : 6 is used it would have lesser corrosive effect on iron and steel. 

8.5 Suitable Combination of Under-Coats, Finishing Coats and 
Characteristics of Plastering Mixes — As a general rule, any coat 
of plaster shall not be stronger than the base or the previous coat. 
Under-coats and finishing coats shall be reasonably related to one 
another and to the structural background in regard to density and 
strength on the one hand and as liability to expansion or contraction 
during setting and drying on the other. 

8.6 Number of Coats — For normal backgrounds, one coat is adequate 
for ordinary finish and two coats for high class finish. However, in 
special situations or where background is very rough and uneven, three 
coats may be necessary. 

8.6.1 Cases where the nature of location of background influences the 
choice with regard to the number of coats are as follows: 

a) Wood lathing normally requires three-coat plaster finish for 
satisfactory results, 

b) Three coats of plaster may be necessary for finishing uneven 
stone masonry, and 

c) In case of plastering on ceiling and sofiit, generally one coat will 
be sufficient but for ceilings of floors or roofs constructed with 
rough stone slabs which are not adequately dressed and where 
there are undulations in the surface two coats will be necessary. 



IS : 2394 - 1984 

8.6.2 The range of coats normally employed for different backgrounds 
are as follows; 

Brickwork 1 or 2 

( Internal and external ) 

Stonework 2 or 3 

( Internal and external ) 

Concrete blocks 1 or 2 

Wood laths 2 or 3 

Soffits and ceilings I or 2 

8.7 Thickness of Plastering — The thickness for plaster work 
exclusive of key or dubbing out shall generally be as given in Table 1. 





TABLE 1 THICKNESS FOR PLASTER WORK 








{ Clause 8.7 ) 








Sl 


Type op Work 




First 


Second 


Third 


No. 






Coat 


Coat 


Coat 


<1) 


(2) 




(3) 


(4) 


(5) 








mm 


mm 


mm 


i) 


Brick masonry: 












a) Single-coat work 




15 


— 


— 




b) Double-coat work 




10 


10 


— 


ii; 


Stone masonry 




15 


10 


— 


iii) 


Stone masonry ( very 
surface ) 


rough 


15 


10 


10 



8.8 Surface Finish — Plasters shall be finished to a smooth surface. 

8.9 Effect of Atmospheric Conditions ~ The ideal conditions for 
application of plaster are gentle warmth coupled with moderate 
ventilation. Extremes of all kinds should be avoided as far as possible. 
The effect of prevailing weather at the time of plastering or during the 
setting, drying and hardening period is similar for lime plaster as for 
cement or cement lime plaster {see also IS : 1661-1972*). 

9* GENERAL PRECAUTIONS IN PLASTERING 

9.1 Rouhgness — The roughness of background improves the bond of 
plaster. This is particularly important in case of soffits and ceilings. A 

♦Code of practice for application of cement and cement-lime plaster finishing 
{first revision). 



IS : 2394 - 1984 

smooth surface may be roughened by wire brushing, if it is not hard; or 
by hacking if it is hard. After roughening the surface care shall be taken 
to moisten the surface sufficiently before plastering otherwise, the freshly 
exposed surface may tend to absorb considerable amount of water from 
the plaster. In case of special backgrounds, wood lath, expanded metal 
lathing, wire netting, etc, may be fixed to provide key to the plaster. 

9.2 Surface Gleaning — The background surface shall be thoroughly 
brushed to remove dust, loose particles of mortar, etc, or efflorescence 
where it has occurred. 

9.3 Dubbing — Dubbing may be necessary where the background is 
very uneven and that unevenness cannot be made up in regular courses of 
plastering. The process of dubbing consists in filling the holes and 
depressions with mortar of the same mix as for the first coat. The 
patches of plaster thus done are left rough so that the subsequent coat 
of plaster would stick to it. 

9.4 Suction Adjustment — Suction is the force by which the plaster is 
held on the surface after it is laid by the plaster's trowel and until it has 
hardened. Without the aid of suction, plaster would creep and slide 
down due to its own weight. On the other hand, very strong suction 
withdraws all moisture from the plaster and makes it weak, porous and 
friable. Careful adjustment of suction is, therefore, very necessary for 
good plastering and may be achieved by wetting the backing suitably if 
it is dry. However, too much water makes it impossible to keep the 
mortar in position till it sets; therefore, the wall shall not be socked but 
only damped evenly before applying the plaster. If the surface becomes 
dry in spots, such areas be moistened again to restore uniform suction. A 
fog-spray may be used for this work. As far as possible plaster work 
shall be so planned, that it is done when the surface of the sides of 
buildings to be plastered are in shade, 

9.5 Control of Cracking — The main reasons for cracking of plaster 
are as follows: 

a) Quick drying of the mortar due to hot weather and low 
atmospheric humidity, 

b) When a strong mix has been used on a weak background, 

c) Lack of bond with the background, 

d) Masonry underneath has not undergone initial shrinkage, 

e) Lack of proper raking of joints, and 

f) Discontinuity in backgrounds, such as change from wall to 
ceiling from concrete to brick work, from clay brick work to 
concrete block work, etc. 

10 



IS : 2394 - 1984 

9.5.1 In case of discontinuity backgrounds, the best treatment would 
be to separate the two portions by a neat cut through the plaster at the 
junction. In the case of discontinuity from wall to ceiling, a cornice that 
would permit slight movement without cracking may advantageously be 
introduced. If it is not proposed to provide a cornice, a straight cut 
through the plaster or a groove joint at the junction may be provided. 

9.5*2 In load bearing construction, cracks are also caused in the top 
floor partitions due to roof movement by variation in temperature. 
Development of such cracks shall be prevented by isolating the top of 
partition from the roof slab. To achieve this, plastering shall not be 
carried over the junctions of partition walls with the roof slab. 

9,5.3 When plaster is applied to provide an unbroken surface over 
board or slab background, the plaster coat bridging the joints is subject 
to higher stresses and any movement in the background will show by 
cracks along the joints. To avoid this, the plaster is reinforced at the 
joints by fixing jute scrim or suitable wire gauge. This treatment may 
still be ineffective if large changes in humidity take place and if thin 
board backgrounds with high moisture movement are used. 

9.6 Avoidance of Surface Grazing — Surface crazing is due to 
excessive shrinkage caused by drying. The mortar tends to shrink on 
hardening, but is restrained by bond with the background which is 
practically immune from movement of brick or stone. The restraint 
to shrinkage causes tensile stress in the plaster which is maximum at the 
skin. If the shrinkage is great, these failures develop into cracks which 
exist through the whole depth of the plaster. In order to prevent this 
formulation, it is necessary to limit the differences in shrinkage and 
thereby reduce the tensile stress to within safe limits. 

9.6.1 Attention to the following points will reduce surface crazing to 
a minimum: 

a) Use of well-graded sand and suitable proportion of various 
ingredients for mortar, 

b) Thorough grinding of mortar and thorough mixing of different 
constituents, 

c) Proper addition of solutions and other materials to improve the 
bending properties of mortar, 

d) Observance of adequate time intervals between successive coats 
so that each successive coat undergoes a portion of its shrinkage 
before the next coat is applied and thus reduces the skin tension 
in the preceding coat, 

11 



IS : 2394 - 1984 

e) Proper workmanship as regards application of different coats, 
and 

f ) Avoidance of quick drying in initial stages. 

9.7 Working Periods with Regard to Setting Properties of 
Mortars — Plastering work shall be completed before the setting protess 
for the mortar has started. All mortars shall be used as soon as possible 
after grinding, preferably on the same day. If eminently hydraulic lime 
( Class A ) is present as an ingredient, the mortar shall be used within 
4 h after grinding. Lime pozzolana mortar shall be used within 24 h of 
grinding. 

10. PRELIMINARY WORK 

10.1 A preliminary inspection shall be made to ensure that the surfaces 
are in a suitable condition for plastering, particularly with regard to their 
evenness and dryness. If dubbing out is necessary, it should be done in 
advance, so that an adequate time interval may be available before the 
application of the first undercoat. 

10.2 Plastering operations shall not be started until necessary fixtures, 
such as frames of doors, windows, etc, are completed and all pipes and 
conduits to be embedded in the wall are installed so that there is no 
necessity to cut the plaster. 

11. PREPARATION OF BACKGROUND FOR APPLICATION 
OF LIME PLASTER 

ILI For durability of plaster it is vital to obtain a satisfactory bond 
between the background and the first plaster coat and also to ensure that 
the bond is maintained subsequently. Necessary preparation of the 
background shall be done to fulfil the requirements mentioned in 11.2 
to 11.4. 

11.2 Except for rough and uneven surfaces all joints in the brick 
masonry on the fair side shall be raked out to depth of not less than 
12 mm while the mortar in the jomts is still green. All joints in the 
brick and concrete block masonry sball be raked out. 

11.3 Roughening and cleaning of the background surface shall be carried 
out as in 9.1 and 9.2. Where necessary dubbing shall be carried out as 
explained in 9.3, 

11.4 The masonry shall be allowed to dry out for sufficient period so 
that initial drying shrinkage is fairly complete and suction adjustment is 
possible during plastering (see 9«4). The background should be 

12 



IS : 2394 - 1984 

moistened before the application of plaster. Differential movements 
between the background and the plaster due to moisture change will 
cause cracking of the plaster, as explained in 9,5. Major part of such 
movements shall be allowed to set in before the plaster is applied, as for 
example, by giving in the case of moisture movement sufficient drying 
interval to the background. In concrete construction backing shall be 
prpperly done for good adhesion of the plaster to the background. 
Hollow concrete blocks and foam concrete blocks shall only be lightly 
wetted before the application of plaster. 

12. PREPARATION OF LIME MORTARS FOR PLASTERING 

12.1 Proportioning — Materials to be used in the preparation of lime 
mortar shall be measured by volume-gauge boxes. Proportioning of lime 
shall be done by measurement of volume as lime putty. In case the 
measurement is done on quick lime or hydrated/dry-slaked lime, their 
quantity shall be such as to yield the required volume of lime, putty. 

Note — The lime in mortar mixes is assumed to be measured as lime putty. If 
it is measured as hydrated dry slaked lime, the proportion of lime in any mix shall 
be slightly higher than that is indicated, and a suitable adjustment shall be made 
as indicated in 12.1.1. 

12.1.1 The actual mass of hydrated lime which a putty contains may 
be determined by using the following formula: 

^4=--^(^p-1000) 

where 

Mb — mass of dry hydrate, 

G = specific gravity of hydrate, and 
Afp = mass of puty. 

12.1.2 The recommended mix proportions for lime mortars for plaster 
work shall be as given in Table 2. 

12.1.3 Quantity of Water — The quantity of water required varies 
depending upon the quantity of lime, the proportion of the mix, nature 
of aggregates and also the weather. 



clependmg upon the quantity oi lin: 
of aggregates and also the weather 

12.2 Grinding 



12.2.1 Lime putty and sand in the specified proportions shall be mixed 
with or without the addition of water on a dry water-tight mixing 
platform. The material shall then be fed into the mortar mill with the 
required addition of water and ground in accordance with V2.2.3. 

13 



IS : 2394 - 1984 



TABLE 2 RECOMMENDED MIX PROPORTIONS 

( Clause 12.1.2 ) 



Sl 

No. 


Type of Goat 


Mix Proportion 
BY Volume 


Glass of Lime 

Conforming to 

Appendix in 

IS : 712-1973* 


(I) 


(2) 


(3) 


(4) 


i) 


Dubbing and lirst coat 
( both for external 
and internal sur- 
faces ) 


1 lime: 2 to 3 sand 

or 
1 lime: 1 pozzolana: 1 
to 2 sand 


AandB 
C 






or 
1 lime: 2 to 3 pozzo- 
lana { for first coat in 
the case of two coat 
work ) 


G 


ii) 


Second coat 


1 lime: 1 pozzolana: 2 
to 3 sand 


G 


iii) 


jVeeru finishing coat 


Lime and fine sand 
ground in equal pro- 
portions 


C 


•Sp, 


ecification for building limes 


( second revision ) . 





12.2.2 If dry material is used, the dry-slaked hydrated lime and sand in 
specified proportions shall be mixed dry first and shall then be fed into 
the mortar mill with the required additions of water and ground in 
accordance with 12.2.3. 

12.2.3 The mortar shall be raked continuously during grinding, parti- 
cularly in the angular edges of the masonry lined mortar mill. Water 
may be added during grinding as required but care shall be taken not 
to add more water than required to bring the material to the required 
consistency. The mixing shall be done till every particle of aggregate 
is coated uniformly with cementitious material. The mortar shall be 
ground for not less than 180 rev in the mortar mill. 

12.2.4 The mortar shall be used as soon as possible after grinding. As 
a rule, mortar shall be used on the day it is made. Lime mortar and 
lime pozzolana mortar remaining unused for over 72 and 24 h respectively 
shall be rejected and removed from the site. All lime mortars after 
grinding shall be kept damp and shall never be allowed to go dry. This 
may be ensured by covering the ground mortar with wet sacks or by 
any other suitable means. Partly set and dried mortar shall not be 
reteriipered for use. 

14 



IS : 2394 - 1984 

12.2.5 Mixing of Lime Pozzolana Mortars — Lime either as dry-slaked/ 
hydrated lime or in the form of putty shall first be mixed with the 
pozzolana in specified proportion and ground in the mortar mill with 
addition of required quantities of water. Where specified sand shall 
then be added to the mix and mixing and grinding repeated till every 
particle of the aggregate gets uniformly coated with cementitious 
material. Lime pozzolana mortar shall be used within 24 h after 
being mixed. 

Note 1 — To improve the binding properties of mortar, gugal ( armyres agal 
locha) at the rate of 1*5 kg/m" of mortar may be added to the mortar for the first 
and second coat when it is being ground. Also a solution o( gur at the rate of 25 g of 
water may also be added to the mortar when it is being worked before plastering. 

NoTB 2 — Fibrous materials, such as cattle hair, hemp, coconut or vegetable 
fibre, etc, may also be added at the rate of 1 kg/m» of mortar to improve its adhesive 
and binding properties which are specially required for undercoats. 

13. APPLICATION OF LIME PLASTER 

13.0 General — It is an advantage to plaster the ceiling first and then 
to plaster the walls starting from the top and working downwards. 
This will permit the removal of scaffolding as early as possible. 

13.1 To ensure even thickness and a true surface, plaster about 
150 mm X 150 mm shall be first applied, horizontally and vertically, at 
not more than 2*0 m intervals over the entire surface to serve as gauges. 
The surfaces of these gauged areas shall be applied in a unifrom surfaces 
slightly more than the specified thickness. This shall be beaten with 
thapies to ensure thorough filling of the joints and then brought to a 
true surface by working a wooden straight edge reaching across the 
gauges with small upward and sideways movements at a time. Finally 
the surface shall be finished off true with a trowel or wooden float to a 
smooth or a sandy granular texture. Excessive trowelling or overworking 
the float shall be avoided. During this process a solution of lime putty 
shall be applied on the surface to make the latter workable. All corners, 
arrises, angles and junctions shall be truly vertical or horizontal as the 
case may be and shall be carefully finished. Rounding or chamfering 
corners, arrises, junctions, etc, shall be carried out with proper templates 
to the sizes required. 

13.1.1 In suspending work at the end of the days, the plaster shall be 
left cut clean to line both horizontally and vertically. When 
recommending the plastering the edge of the old work shall be scrapped 
clean and wetted with lime putty before plaster is applied to the adjacent 
areas to enable the two to properly joint together. Plastering work shall 
be closed at the end of the day on the body of wall and not nearer than 
1 50 mm to any corners or arrises. It shall not be closed on the body of 

15 



IS : 2394 - 1984 

feiiiuie such as plaster bands and cornices nor at the corners or arrises. 
Inhere shall be no horizontal joints in plaster work on parapet tops and 
copings, as these invariably lead to leakages. No portion of the surface 
shall be left out initially to be patched up later on. 

13.1.2 Some times, ends of scaffolding bailies have to be housed in the 
wall which is being treated with plaster. In such cases, after the bailies 
are taken out, holes left in the wall shall be filled up with brick and 
mortar and the patch plastered up true, even and smooth in conformity 
with the rest of the wall so that no sign of any patch work shows out. 

13.2 One Coat Plaster Work 

13.2.1 Masonry walls on which plaster is to be applied directly, shall 
be clean and dry with the joints raked to a depth of at least 12 mm 
before applying the first coat. The surface shall be damped evenly to 
control suction which is an essential treatment for securing first class 
work. The plaster shall be of specified thickness and carried out to the 
full length of wall on to the natural breaking points like doors and 
windows. 

13.2.2 The mortar used for plastering shall be stiff enough to cling 
and hold when laid; for ceilings the mix is required to be stiffer than that 
us^d for walls, on soihts the mortar shall be laid in long even spreads 
outwards from the operator overlapping each trowel full and using 
su/Iicient pressure to force it into intimate contact with the background. 
On walls the mortar shall be laid in long even spreads upwards and 
across, overlapping each trowel full, using sufhcient pressure to force it 
into intimate contact with the background. 

13.2.3 On relatively smooth background the mortar may have to be 
d;;shed on to ensure adequate bond for it when applied with a trowel. 
Dashing of the first coat aids in securing intimate bond by excluding air 
which miglu otherwise be trapped behind the plaster. The dashing of 
the first coat shall be done using a strong whipping motion at right 
angles to the face of the wall. 

13.2.4 The plaster shall be laid in a little more than the required 

thickness and levelled with a wooden fioat. The plaster shall be 
trowelled hard and tight forcing it into joints to obtain a good bond and 
surface rubbed smooth with a plaster's trowel. 

13.2.5 The plaster shall be water cured as described in 14. 

13.3 Two Coat Plaster Work 

13.3.1 First Coat —The first coat of the specified thickness shall be 
np[)lied in a manner similar to one coat piaster mentioned in 13.2. 

\G 



IS 12394-1984 

Before the first coat hardens its surface shall be beaten up by edges of 
wooden tapers and close dents shall be made on the surface. This helps 
the plaster in several ways : the cracks are closed, the mortar is compacted 
and driven home into the joints and the dents serve as a key to the 
subsequent coat. The subsequent coat shall be applied after this coat 
has been allowed to set for 3 to 5 days depending upon weather 
conditions. The surface shall not be allowed to dry during this period. 

13.3.2 First Coat on Wooden Lath and Metal Lathing — The mortar shall 
be stiff enough to cling and hold when laid and shall then be applied by 
laying and spreading diagonally across the lath work overlapping each 
trowel full and using sufficient pressure to force it through the lath work 
to enable it to lap on the other side. The material shall be laid as 
uniformly as possible. The average thickness shall not exceed 10 mm. 
This coat shall be allowed to stand to get firm before denting, 

13.3.3 Second Coat — The second coat shall be completed to the specified 
thickness in exactly the same manner as for the first coat. The finshing 
coat shall be laid with a mason's trowel to an average thickness of 5 mm. 

13.3.4 Curing shall be done as described in 14. 

13.4 Three Coat Plaster Work — The first two coats shall be applied 
in a manner as explained in 13.2 and 13^3. The third coat shall be 
completed to the specified thickness in the same manner as for the second 
coat and shall be cured as described in 14. 

14. CURING 

14.1 Curing shall be started 24 h after finishing the plaster. The plaster 
shall be kept wet for a period of 7 days. During this period it shall be 
suitably protected from external damages. The dates of plaster shall be 
legibly marked on the various section of the walls so that curing for the 
specified period thereafter can be watched. 

15. SPECIAL FINISHES 

15.1 Madras Plaster — This is a special plaster finish applied in three 
or more coats to obtain a smooth polished surface in places where shell 
lime and fine sand are easily available. 

15.2 First Coat — The first coat of lime plaster shall be applied to the 
wall as specified in 13.2. This shall be allowed to set for 2 or 4 days and 
then the surface scoured thoroughly in diagonal lines crossing, each other. 
The plaster shall be kept constantly watered till it is nearly set and then 
the second and third coats may be applied as in 15.3 and 15.4. 

17 



IS: 2394 -1984 

15.3 Second Goat — One coat, about 5 mm thick, of the mix specified 
in 15.3.1 shall be applied and brought to an exact level surface with long 
wooden floats or where required, with curved moulds. The surface of 
the undercoat shall be watered, if necessary, before applying this coat. 

15.3.1 The mix shall consists of the following: 

Parts by Volume 
Shell lime (.slaked) 12 

Fine white sand 9 

Powdered marble 1 

The sand shall be ground very fine. The marble also shall be 
ground fine and sifted through muslin. The materials shall be mixed 
with water and kept in a heap, well wetted for 2 days. 

15.4 Third Goat — The same mix as used for the second coat shall be 
ground on flat stone slabs with stone rollers to the consistency of fine river 
mud and applied to a thickness of about 2 mm over the second coat, 
be wetted before hand. 

The surface of the third coat shall be polished first with trowels and 
then with very hard smooth stones. While the polishing operation is in 
progress soap stone powder contained in the muslin bags shall be dusted 
on the surface. The operation shall be continued till a high smooth 
polish is obtained. 

15.5 Curing shall be done as explained in 14. 

16. REPAIRS 

16.1 Cutting — The mortar of the patch where the existing plaster has 
cracked, crumbled and sounds hollow when tapped gently on the surface 
shall be removed. The patch shall be cut out to a square or rectangular 
shape at the places marked on the wall. The edges shall be undercut 
slightly to provide a dove-tailed key for the patch plaster. 

16.2 Preparation of Surface — The masonry joints which become 
exposed after removal of old plaster shall be racked out to a minimum 
depth of 12 mm in the case of brick work and 20 mm in the case of stone 
work. The raking shall be carried out uniformly with a racking tool and 
loose mortar dusted off. The surface of the masonry shall then be 
scrubbed with wire brushes to clean it of all mortar. The surface shall 
then be thoroughly washed with water and kept wet before plastering is 
commenced. . 

18 



IS : 2394 - 1984 

With regard to concrete surfaces the same shall be thoroughly 
scrubbed with wire brushes after the plaster has been cut out and surface 
washed and cleaned. 

16.3 Application of Plaster — The method of application shall be as 
described for one coat plaster work ( see 13.2 ). The surface shall be 
finished even and flush with the old surrounding plaster. 



19 



INTERNATIONAL SYSTEM OF UNITS ( SI UNITS ) 



Base Units 








Q.TTANTITy 


Unit 


Symbol 




Length 


metre 


m 




Mats 


kilogram 


kg 




Time 


second 


s 




Electric current 


ampere 


A 




Thermodynamic 


kelvin 


K. 




temperature 








Luminous intensity 


candela 


cd 




Amount of substance 


mole 


raol 




Sopptementary Units 








Quantity 


Unit 


Symbol 


. 


Plane angle 


radian 


rad 


'. -^ 


Solid angle 


steradian 


sr 




Derived Units 








QpANTITT 


Unit 


Symbol 


Dbtinition 


Force 


newton 


N 


IN =1 kg.m/s« 


Energy 


joule 


J 


1 J « 1 N.m 


Power 


watt 


W 


1 W « 1 J/s 


Flux 


weber 


Wb 


1 Wb « 1 V.s 


Flux density 


tesla 


T 


IT =1 Wb/m» 


Frequency 


hertz 


Hz 


1 Hz - 1 c/s (s-M 


Electric conductance 


Siemens 


S 


IS -» 1 A/V 


Electromotive force 


volt 


V 


IV -=1 W/A 


Pressure, stress. 


pascal 


Pa 


1 Pa = 1 N/m« 




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